Though we may think we know what lies beneath the ground under our own feet, there are plenty of things that have remained buried that we’re unaware of. This includes anything from as small as treasure to entire cities, lying under layers of rock and dirt with only a dim memory of them on the surface in the form of legends and/or ancient historical records. Yet every now and then, some of these hidden underground secrets reveal themselves to us mere surface dwellers through natural accidents. These range from cave-ins caused by storms or earthquakes to accidental discoveries made by ordinary people.

With that said, the significance of these subterranean discoveries only becomes relevant in relation to the discovery itself and its historical context. For instance, a coin that was buried may seem valuable in of itself. But unless it’s an artifact from the past or worth a lot in terms of value, it’s nothing more than a coin. Plus, there are plenty of claims of things that have been found underground which haven’t been properly verified due to their outlandishness in terms of authenticity. Still, it does open up a whole other world for us and changes our perception of things.

23 Yerba Buena Cove Ships

When the California Gold Rush was in full swing, all kinds of people came by land or by boat. Those that came by boat often never came back, thus leaving the boats “Abandoned as their passengers and often their entire crew left in search of gold” according to the Chiltern Thrust Bore website. This was especially the case at Yerba Buena Cove, where many ships were anchored and left to decay over time. Eventually, Yerba Buena Cove became as developed as the downtown area of San Francisco and so most of the ships were buried underneath and/or uncovered in some cases.

22 Taklamakan Desert Secrets

Located in the western part of China, this desert is one of the larger ones there if not the largest. Yet what makes this desert particularly special is what’s buried beneath it. According to Ancient Pages, “There were houses and temples here” long ago. Though as the above picture demonstrates, some of these structures are now starting to be uncovered by archeologists. Aside from being large in terms of size, the Taklamakan is also known to be “The world's second largest shifting-sand desert” Ancient Pages states. So knowing that, it’s no wonder these structures lay buried for so long.

21 Track 61

Among the various train tracks that branch out from the Grand Central Terminal’s network in New York City, there is one that is well-hidden. Simply known as Track 61, it “Has a secret entrance and a passage that leads to a lift from the well-known Waldorf-Astoria Hotel” Gunaxin states. The person who primarily used this track was Franklin D. Roosevelt, which served a number of purposes for him. It was not only convenient in terms of travel from the hotel to the train station, but the secret track also allowed him to avoid the press and public.

20 Derinkuyu

Discovered in the 1960s, this underground complex near Cappadocia, Turkey, is quite the marvel to behold. Described as having “A most sophisticated infrastructure and the accommodation built” Ancient Pages says, it’s clear that this subterranean dwelling was meant to be occupied “For long periods of time”. Through various excavations over the years, archeologists have determined that it was used by multiple groups that occupied the area at different points in history as a shelter of sorts during times of war. So with that in mind, it does make one appreciate the architects who built Derinkuyu regardless of who they were.

19 Palais de Chaillot Underground Theatre

As spooky as the Catacombs of Paris are, there are even stranger mysteries afoot. For instance, “A fully equipped cinema” was found inside an uncharted cavern according to Chiltern Thrust Bore. Now this didn’t just include a projector and accompanying screen, but also an underground bar/restaurant nearby. So one would assume this was an underground get-together to watch controversial films that were banned. But in actuality, the films recovered were “1950s noir films as well as recent thrillers” Chiltern Thrust Bore states and a mysterious note that said, “Do not try to find us” was left behind too.

18 Underground Orvieto Pyramid

Now as strange as finding a functioning movie theater underground may be, that’s nothing compared to an underground pyramid. To give some context, there are “A series of underground structures connected by tunnels” underneath Orvieto, Italy, according to Ancient Pages. Though it may be small city-wise, Orvieto is historically significant because many of the buildings and the underground network date back to when Italy was predominantly occupied by the Etruscans. Within this underground network, the pyramid-shaped structure was found “By an international team of archaeologists” as stated by Ancient Pages who don’t know what its purpose is yet.

17 Motala Lake Structure

Up in Sweden, there is a place called Motala which resides near a lake. But there’s also a dry lakebed nearby that dates back to prehistoric times. So an excavation by archaeologists went underway in 2009, according to Cracked, where they found a stone structure. Initially seen as mysterious, this structure’s purpose became more complex once the archeologists uncovered several things within it which included multiple remains. Their inconsistent ages and fractured state left archeologists puzzled, leading to multiple theories in turn. These ranged from being morbid warrior trophies to unusual burial practices done by natives.

16 Underground City of the Grand Canyon

Given how vast the Grand Canyon is, there’s only so much that can be explored. This issue is further complicated when one has to take into account the areas that are off-limits for federal reasons, so it just makes the place more mysterious to some. Yet one of the strangest mysteries associated with the Grand Canyon came out of an article published in 1909 which reported “The discovery of a great underground citadel” Ancient Pages states. This in turn has implicated the possibility of a hidden city that lies beneath the ground, though some think it’s merely a hoax.

15 Lost Underground City of Missouri

While the Grand Canyon itself is certainly amazing enough to spark one’s imagination into thinking that there could be an underground city beneath it, regardless if it’s real or not, the same might not be said about Missouri. Apart from its cities and museums, there’s not a lot going for it geography-wise. Yet in the 1800s, an odd story appeared where two men from Moberly, Missouri, claimed they “Discovered an ancient wonderful lost city… at the bottom of a coal shaft” according to Ancient Pages. While the authenticity of this story is dubious, there is a place called SubTropolis.

14 Haut de la Garenne Underground Rooms

Though orphanages are a good thing to have as a place of refuge for children who were abandoned by their parents, bad things can happen in these places too. One such example can be found at the Haut de la Garenne, an orphanage located in the Bailiwick of Jersey which is part of the Channel Islands that are near the coast of Normandy, France. Here, it was discovered in 2008 during a police investigation that, “An underground network of four rooms” existed where “The orphans were punished” in severe ways from the 1940s up to the 80s according to Gunaxin.

13 Indian National Library Chamber

Within the Indian National Library in Calcutta (now known as Kolkata), India, an interesting discovery was made by an archeological survey while the building was being reconditioned. According to Gunaxin, it consisted of “A hidden chamber from the Indian National Library” to the nearby Belvedere Estate. The purpose of this chamber is currently unknown, since the archeological survey couldn’t find an entrance into it nor were they allowed to make an entry due to the Belvedere Estate’s classification as a historic building. Some theories about it have ranged from being a place where convicts were stored to having hidden treasures.

12 The Chamber of nightmares

Though his legal name was Herman Webster Mudgett, history knows him by another name: H. H. Holmes. During the late 1800s, he owned a hotel and drugstore in Chicago. But the hotel wasn’t what it seemed, much like the man. For instance, it was built by Holmes “Using the money he had gained from fraud” and other unscrupulous methods as stated by Gunaxin. Then when Holmes was arrested for being involved in crimes of a serial nature, more secrets were uncovered. This included a secret chamber in the basement of the hotel “Filled with surgical devices and instruments” Gunaxin states.

11 Mont Sainte-Odile Tunnel

Located in a mountainous region of France, the Mont Sainte-Odile monastery became the center of a strange mystery where books were vanishing from the library despite the place being well-sealed. After the authorities showed up, “They determined that a certain sector of the library could be moved to reveal a secret passage” according to Gunaxin. Sure enough, they were right and caught the thief who turned out to be a teacher from the area. It turned out he found a map of “The secret passage to the monastery’s archives” Gunaxin says and took advantage of it.

10 Passetto di Borgo

For those familiar with The Da Vinci Code books, or even the movies, this name should sound familiar. If it doesn’t, here’s what it basically is: a tunnel that, “Stretched along the old Vatican wall which connected the city of Vatican to Sant’Angelo Castle” or the Hadrian Mausoleum as it’s also called according to Gunaxin. Dating back to the 1200s, this tunnel was a lifesaver for many a Pope in Vatican City who used it to escape potential threats such as invasions and sieges. It also has parts that go below certain buildings, archways, and even inside the wall itself.

9 Northern Europe Bogs

In the northern parts of Europe, such as Britain and Ireland, there are large swaths of bogland which tend to be avoided in case of possibly sinking into the peat that makes up a majority of the bog itself. Yet for centuries, farmers have harvested peat to be used as a substitute for firewood especially in areas where trees are relatively scarce. This tradition still continues today, though every now and then an unexpected discovery is made. Often these are remains that are well-preserved due to “The high acidity, low temperature and lack of oxygen” in bogs Cracked states.

8 Mount Owen Caves

Thanks to horror movies like The Descent, exploring caves has become yet another thing to be afraid of. After all, it’s basically wandering around the dark with nothing more than a light or two in a seemingly empty cave that might hold some unexpected surprises. Such a surprise occurred when a 1980s expedition into the caves of Mount Owen, which is in New Zealand, found “The 3,000-year-old remains of an upland moa” according to Cracked. Similar to an emu in terms of its appearance, the Upland Moa was an ancient species of bird that went extinct long ago.

7 Mt. Tsurugi Tunnels

While many an expedition has uncovered some unpleasant discoveries in the past, the strangest expeditions are arguably the ones that stop for no reason making us wonder what they could’ve found that made them halt exploration. Apparently, such was the case with an expedition to Mt. Tsurugi in Japan that occurred in the 1930s where a series of tunnels were discovered among other things. According to Ancient Pages, this helped to prove a “Theory that ancient people modified the peak of Mt. Tsurugi in order to hide something significant”. Though the excavations continued for three years, they abruptly stopped altogether.

6 Dura-Europos Siege Tunnels

In the desert region of Syria, lie the ruins of an ancient city called Dura-Europos which was occupied by the Romans after they took it from the Parthians, the original occupants. Unfortunately, the Romans weren’t able to hold onto it for long as they were overtaken by another group called the Sassanians. While archeologists were investigating this place in the 1930s, they came upon a series of tunnels with several remains. But what was strange were the “Traces of sulfur and bitumen all along the walls” as described by Cracked implying an early form of chemical warfare was used.

5 Underground Labyrinths of Egypt

Just when it seemed all the secrets of Ancient Egypt had been exposed or debunked, another mystery has emerged. In many ancient texts, there is a place that’s described as a “Labyrinth” which is “Believed to be an enormous collective tomb” as stated by Ancient Pages. Numerous expeditions have occurred over the centuries to try and find this place, though none of them have been able to pinpoint exactly where it is. The closest estimate so far has been Hawara, a site which consists of a pyramid though there used to be a temple nearby that might have inspired the “Labyrinth”.

4 Lake Seydozero Ruins

Way up north in Russia lies an area called the Kola Peninsula where the lesser-known Lake Seydozero resides which means “Sacred” in the language of the indigenous Sami people according to Ancient Pages. Now it may not look like much, judging by the above picture alone, but this place has become a center for a number of bizarre theories. For instance, it’s believed that, “The ruins of an ancient observatory and mysterious rock inscriptions in Russia’s Northwest are vestiges of the ancient Hyperborea civilization” Ancient Pages says. Whether claims like this are true or not is hard to say.